1. Field of the Invention
The present invention relates to a manufacturing method for platinum counter electrode applicable to dye-sensitized solar cells (DSSC), and more particularly to a method that comprises polyol reduction to fabricate platinum nanoparticle solution first and dip-coating a conductive substrate in the solution at low temperature thereof to manufacture a self-assembled platinum counter electrode.
2. Description of the Prior Art
Dye-sensitized solar cells (DSSC) are promising devices for energy conversion to generate clean renewable energy and to diminish emissions of greenhouse gases with the advantages of low cost, simple processing and efficient performance. Overall, platinum electrode is considered to be the most promising component to give record device efficiency of power conversion because of its great catalytic activity. However, since pure platinum is very expensive, alternative materials, for example, platinized counter electrode (CE) formed on a substrate that is advantageous of being easily made and adopted to afford mass production are thus proposed nowadays in order to replace the pure platinum electrode so as to save the production cost and become widely used in the market.
In tradition, to prepare a thin layer of platinum on a transparent conducting oxide (TCO) substrate as CE, several strategies including thermal deposition (TD), sputtering deposition (SD), and chemical reduction method have been applied. However, TD requires subsequent annealing at a high temperature such as 385° C., which makes it infeasible for flexible devices; SD requires processing under an ultrahigh vacuum condition with much Pt wasted in the chamber, which makes it unfavorable for mass production. Chemical reduction must be in process of adequate stabilizer involved, such as polyvinyl pyrrolidone (PVP) or other surfactant or protective agent in order to stabilize the reduction kinetics and lower its reaction rate such that no particle aggregation will be formed. Although the use of stabilizer may result in less consumption of precious metal, nevertheless, additional post-heating steps must be utilized to remove these stabilizers which may be attached to a surface of the electrode substrate, such that metal particles can be adhesive to the electrode substrate more tightly without any stabilizers in between, and the conventional issues that series resistance may go up and power efficiency may be lowered will be avoided. However, it shall be noticed that after the post-heating steps are adopted, a distribution of Pt nanostructure is not formed homogeneously and uniformly, but aggregated to form a plurality of islands, which may cause a huge waste of precious metal, thereby resulting in high production cost. Meanwhile, the post-heating treatment is not only time and money consuming, but also inapplicable to mechanical rigidity (adhesive strength) to improve the enduring stability, especially for flexible devices. On account of above, it should be obvious that there is indeed an urgent need for the professionals in the field for a new manufacturing method to be developed that can effectively solve those above mentioned problem occurring in the prior design.